The present invention relates to tennis ball testers and more particularly to a portable and manually operated lightweight tennis ball tester.
The primary purpose of a tennis ball tester is to check the quality of a tennis ball to see if it meets the standards required for play established by the United States Tennis Association. There are large elaborate and expensive machines used by the tennis ball manufacturers to test their newly produced balls. Two leading tennis ball manufacturers have suggested that an acceptable field test is to drop the ball from a height of 100 inches (8 feet, 4 inches) onto a hard surface. The tennis ball must bounce 53 inches to be considered good. This is an impractical test to perform on a tennis court because of the height and the weather factors. Tests show it takes a considerable amount of pressure to compress a tennis ball to a point where an accurate dependable reading can be obtained to determine if the ball meets the requirements for play. The following ate objective of a tennis ball tester.
1. The tester should be lightweight and portable.
2. The testing of the tennis ball should be quick easy and reliable.
3. The tester must be capable of being carried in a tennis bag and will receive some abuse so it should be durable.
4. A reasonably priced tester is a very important feature of the tester that all other testers lack. The cost of a container of three balls is approximately $2.00. We must approach the tennis ball tester with common sense. The market is limited to the more serious players and those who may purchase it as a gift. Why buy an expensive tester when one can purchase a new container of balls for $2.00. This narrow market and the low cost of new balls make it a risky adventure for an investor. Therefore, the tennis ball tester must be inexpensive. At present there isn""t a tennis ball tester on the market because of impractical design and prohibitive manufacturing costs of the prior art. The prior art found in a search is found to be defective in most or all of the conditions essential to a practical low price tennis ball tester outlined hereinabove that would appeal to the limited market available.
U.S. Pat. No. 5,639,969 by the Adamo presents several problems that make it impractical. The device of this patent requires a great amount of force to compress a tennis ball to a size that an accurate reading of its condition may be taken. In this device pressure must be applied directly to the ball without benefit of any mechanical advantage. In the Adamo device one must overcome the spring to squeeze the ball through a small angular ring. The weaker player will find it difficult, if not impossible, to force the ball through the ring. In this device, the player must select one of the three gauges to determined the condition of the balls"" Knapp. There are very small difference in a tennis ball""s Knapp. When any testing device relies on an opinion, the accuracy of the device must be questioned.
U.S. Pat. No. 5,837,889 to Slenker measures the pressure difference between balls. But it fails to identify the balls with the proper pressure to meet the standard of play. If a used ball has less pressure than a new ball it still may meet the pressure requirement, or play requirement. The scale on this device does not have a marker line to indicate a ball has adequate pressure for play. It is not sound engineering to expect an accurate reading from a cork friction pad that is hand tightened by a wing screw to calibrate the gauge. Tightness is dependent on each individual hand. The flexible arm which must bow over an 8 inch span can also lead to inaccurate and inconsistent readings. Aside from all the engineering and mechanical defects a considerable investment must be made in tooling, molds and machining of the Slenker device. As mentioned earlier, tennis ball testers have a limited market and these tooling costs would deter any investor.
U.S. Pat. No. 5,567,870 to Harris fails to solve the tennis ball testing problem in several areas. Testing has shown that to get an accurate reading on a tennis ball it must be compressed or indented close to approximately halt its diameter. The Harris device does not penetrate the ball with sufficient depth to get readings which would be accurate and consistent. A great amount of pressure is required to probe deeply into the ball. This requires a torsion spring of considerable torque to force the plunger to an adequate depth. This demands a great amount of hand grip strength which the average person does not have. As state above, the plunger must penetrate deeply into the ball. This is not accomplished by the Harris device. The length of travel of the plunger requires a special type of pressure gauge. The pressure gauge shown is not available as a standard off the shelf item. A special gauge is required to meet these specifications. An unworkable mechanics combined with the high cost of special tooling, molds and a custom made gauge make the Harris device an unsound venture to pursue for an investor.
U.S. Pat. No. 5,511,410 to Sherts discloses a gear rack pinion and spring as his basic components. In this embodiment there is no mechanical advantage to the operator inserting the ball. A very strong spring must be employed to probe deeply into the ball for an accurate reading of its pressure. The operator must overcome the spring tension. You are also inserting the ball in a vertical plane while the sensing stem must react in a horizontal plane. This results in great pressure required in inserting the ball and more resistance on the lower bearing surface of the sensing stem.
The Sherts patent offers alternate designs, but they all lack the mechanical advantage required as well as other shortcomings. It is claimed in this patent that the ball tester can be for other types, such as golf balls. Balls for other sports are radically different. To accommodate other balls in this device is impractical and lessens the accuracy of the unit. Sherts device as well as the other embodiments does not establish a minimum standard for a ball playability. A new ball is used as a standard which means that any ball that fails to match the new ball fails the test. A ball still may meet the standard after hours of use. The cost to produce Sherts devices is prohibitive. The special gear rack and pinion must be made along with a special enclosure. This calls for special tooling and the cost is not justified by the limited market.
U.S. Pat. No. 5,291,774 to Puckman Jr. discloses a tester that determines the playability of a tennis ball by the amount the ball is compressed by a 6 pound weighted arm. As stated earlier, in reviewing previous patents a tennis ball is a highly pressurized sphere. A 6 pound weight would not compress the ball to a degree that can be accurately read even at 5 times the length of the compression arm. The 6 pound weight of the arm combined with the additional components make it too heavy to be a portable tester. It is stated in the Puckman patent in column 2, line 5 that the placement of the scale xe2x80x9cplay zonexe2x80x9d is for a new ball and the rest of the scale may be arbitrarily used depending on the level of play. It can only be assumed that the players may set their own standard for the playability of a ball. This poses the question of why have a ball tester if it is not going to identify a used ball that still qualifies to meet the United States Tennis Associations standard.
U.S. Pat. No. 5,222,391 to Reenstra introduces a complex electronic device. This gauge is too sophisticated for the task of testing the ball. It consists of an electronic system with a delicate electronic pressure sensitive sensor plate. This is to detect small changes in the ball size under pressure, Carrying this unit in a tennis bag will subject the unit to vibration, heat on a tennis court and grit on the clay courts. The electronic and sensor plates are critical elements of this approach and its dependability and accuracy are in question. There seems to be no method of calibrating this gauge by the tennis layman. The requirements of a battery add to its weight and maintenance problem. Failure of one of the many electronic components present a problem to a player. In a mechanical tester, it is much easier to detect a failed part than in a complex electronic device. This unit would be costly to produce for the available market.
An object of the present invention is to provide an improved portable and manually operated lightweight tennis ball tester overcoming the disadvantages of the above sited prior art tennis ball testers.
Another object of the present invention is to provide a tennis ball tester that is lightweight, portable, easy to use, reliable and that may be carried in a tennis bag which requires durability.
Still another object of the present invention is to provide a portable and manually operated lightweight tennis ball tester that is reasonably priced.
The basic design of the tennis ball tester disclosed herein lends itself to simple fabrication which can be accomplished in a sheet metal shop. There is no expensive tooling dyes, castings or molds required to produce this unit.
A further object of the present invention is to provide an inexpensive tennis ball tester that would be a sound venture for an investor to pursue.
Still a further of the present invention is to provide a tennis ball tester that has a highly leveraged toggle system which when closed activates the tester to indicate the ball condition on a gauge.
A feature of the present invention is a portable and manually operated lightweight tennis ball tester comprising a housing for receiving at least one tennis ball to be tested, a pair of bars disposed in the housing in a substantially parallel relationship, each of the pair of bars being disposed on opposite sides of the at least one tennis ball; force applying means coupled to one of the parallel bars and extending out of one end of the housing to enable applying a force to the at least one tennis ball; and gauge means coupled to the other of the pair of bars to provide an indication of whether the at least one tennis ball meets the standard of play established by the United States Tennis Association.